Step 1: Understand a short circuit.
A short circuit happens when two points of different voltage get connected by a path of very low resistance, often when bare wires touch. The current then skips the normal device.
Step 2: Recall Ohm's law.
Ohm's law says current $I = \dfrac{V}{R}$, where $V$ is the voltage and $R$ is the resistance.
Step 3: See what happens to R.
In a short circuit the resistance drops to almost nothing, so $R \to 0$.
Step 4: See what happens to the current.
Since current is voltage divided by resistance, a very small $R$ makes $I$ very large. So the current shoots up.
Step 5: Note the effect.
This huge current makes the wires very hot. It can melt wires, damage appliances, and even start a fire. This is why we use fuses and circuit breakers.
Step 6: Check options and conclude.
It does not become small, stay the same, or just keep changing - it rises sharply. So during a short circuit the current increases greatly.
\[ \boxed{\text{Increases greatly}} \]